Sesquiterpene Coumarins, Chromones, and Acetophenone Derivatives with Selective Cytotoxicities from the Roots of Ferula caspica M. Bieb. (Apiaceae)

Abstract

In search of selective cytotoxic compounds from Ferula species as potential leads for the treatment of various cancer diseases, a bioactivity-guided isolation study was performed on the roots of Ferula caspica M. Bieb. COLO 205 (colon), K-562 (leukemia), and MCF-7 (breast) cancer cell lines were used to monitor the cytotoxic activity of column fractions and determine the IC50 value of the active compounds. In addition to the seven known (5–11) compounds, four previously unknown compounds: kayserin A (1), kayserin B (2), 8′-epi-kayserin B angelate (3), and 3-epi-ferulin D (4) were isolated from the dichloromethane extract of the roots of F. caspica. Structure elucidation of the isolated compounds was carried out by extensive spectroscopic analyses such as 1D- and 2D-NMR spectroscopy, High-Resolution Mass Spectroscopy (HRMS), IR spectroscopy, and UV spectroscopy. Although all of the isolated compounds showed various degrees of cytotoxic activity on COLO 205, K-562, and MCF-7 cancer cell lines, the most potent compounds were identified in the following order: 1-Hydroxy-1-(1′-farnesyl)-4,6-dihydroxyacetophenone (HFDHAP, 11), 3-epi-ferulin D (3EFD, 4), and 7-desmethylferulin D (7DMFD, 6). The cytotoxic activities of all three compounds were more potent than that of the reference compound cisplatin (Cis) against all tested cancer cell lines. Still, only HFDHAP (11) was more potent than the reference compound doxorubicin (Dox) against the MCF-7 cancer cell line. The mechanism of action of these three compounds was investigated on the COLO 205 cell line. The results indicated that compounds 4, 6, and 11 trigger caspase-3/8/9 activation and suppress the anti-apoptotic protein, Bcl-xL. Molecular docking studies confirmed the interactions of the three cytotoxic molecules with the active site of the Bcl-xL protein.